2016 AAPM Annual Meeting
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Session Title: Dosimeters for QC in Diagnostic Imaging
Question 1: Which of the following statements regarding ion chambers used in Diagnostic Radiology is incorrect?
Reference:Diagnostic Radiology Physics : A Handbook for Teachers and Students, DR Dance, S Christofides, ADA Maidment, ID McLean, KH Ng, International Atomic Energy Agency, 2014, 529-533
Choice A:In Mammography, parallel plate ion chambers with a thin entrance window are typically used.
Choice B:Cylindrical pencil type ion chambers are mostly used for CT and dental dosimetry.
Choice C:Cylindrical and spherical ion chambers have negligible directional dependence.
Choice D:CTDI ion chambers are designed to produce correct readings when partially irradiated.
Choice E:Most ion chamber dosimeters used in Diagnostic Radiology are sealed chambers.
Question 2: Many modern ion chamber dosimeters automatically convert readings (electrical charge or current) to air kerma by correcting for various factors. Which of the following factors is NOT corrected for?
Reference:Diagnostic Radiology Physics : A Handbook for Teachers and Students, DR Dance, S Christofides, ADA Maidment, ID McLean, KH Ng, International Atomic Energy Agency, 2014, 526-527
Choice A:Atmospheric temperature.
Choice B:Atmospheric pressure.
Choice C:X-ray beam spectrum.
Choice D:Exposure rate.
Choice E:ION recombination.
Question 3: The following is a list of important properties of dosimeters. Solid state dosimeters tend to perform worse in which regard, when compared to ion chambers?
Reference:Diagnostic Radiology Physics : A Handbook for Teachers and Students, DR Dance, S Christofides, ADA Maidment, ID McLean, KH Ng, International Atomic Energy Agency, 2014, 528-530
Choice A:Linearity.
Choice B:Sensitivity.
Choice C:Energy Dependence.
Choice D:Leakage current.
Question 4: There are various definitions of x-ray tube peak voltage. Which of the following has been proposed as the standard quantity of kVp?
Reference:Diagnostic Radiology Physics : A Handbook for Teachers and Students, DR Dance, S Christofides, ADA Maidment, ID McLean, KH Ng, International Atomic Energy Agency, 2014, 546-547
Choice A:Practical peak voltage.
Choice B:Absolute peak voltage.
Choice C:Effective peak voltage.
Choice D:Average peak voltage.
Question 5: Which of the following is a correct statement regarding solid state dosimeters?
Reference:Diagnostic Radiology Physics : A Handbook for Teachers and Students, DR Dance, S Christofides, ADA Maidment, ID McLean, KH Ng, International Atomic Energy Agency, 2014, 536-537
Choice A:Solid state dosimeters are less susceptible to radiation damage compared to ion chambers, and therefore need less frequent recalibrations.
Choice B:Solid state dosimeters tend to be more temperature and pressure dependent than ion chambers are.
Choice C:Most commercial solid state dosimeters at the present time are based on the MOSFET technology.
Choice D:Most commercial solid state dosimeters include backscatter and sidescatter in their readings.
Question 6: All dosimeters used in clinical environment should have a calibration traceable to a recognized standard. Which of the following statements regarding the calibration process is correct?
Reference:Diagnostic Radiology Physics : A Handbook for Teachers and Students, DR Dance, S Christofides, ADA Maidment, ID McLean, KH Ng, International Atomic Energy Agency, 2014, 542-546
Choice A:Primary standards dosimetry laboratories (PSDLs) employ free air ionization chambers for the measurement of absorbed dose traceable to the fundamental SI unit (Gy).
Choice B:The secondary standards dosimetry laboratories (SSDLs) calibrate their reference instruments at PSDLs and use these as their local dosimetry standards.
Choice C:Most SSDLs use the substitution method to determine the calibration coefficient.
Choice D:A general purpose dosimeter is typically calibrated at the RQR5 beam condition, and correction factors are obtained for other RQR beam qualities.
Choice E:All of the above.
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